Jerry S. Hubbard

The Viking Carbon Assimilation Experiments: Interim Report

A synthesis of organic matter from atmospheric carbon monoxide or carbon dioxide, or both, appears to take place in the surface material of Mars at a low rate. The synthesis appears to be thermolabile and to be inhibited by moisture.

Laboratory simulations of the pyrolytic release experiments: An interim report

SummaryDuring its operation on Mars the pyrolytic release experiment (PR) detected the fixation of small amounts of CO2 and/or CO. Laboratory simulations of the experimental conditions were made in an attempt to substantiate the previous conclusion that these reactions were chemical rather than biological. The selection of model substrata for these tests was based on the known properties of the Martian surface material. After pretreatment and incubation under various conditions, pyrolytic analysis was used to indicate the extent of surface catalyzed conversion of14CO2 or14CO to14C-organic compounds. This abiotic synthesis was detected in experiments with three iron oxides, viz. hematite, magnetite and maghemite. When the incubation atmosphere was supplemented with water vapor, the levels of synthesis were in a range comparable to that detected in the Viking PR tests. An abiotic synthesis was also detected in experiments with a mixture of clays and minerals (Mars analog soil) or with montmorillonite artifically enriched in iron. With either substratum the reaction appeared to be the result of a photocatalytic synthesis of14C-organics from14CO and surface hydroxyl groups. This process was not dependent on the presence of water vapor in the incubation atmosphere. Although a duplication of the Viking data has not been achieved, these findings support the abiotic interpretation of the PR results.

Biosynthesis of acyclic methyl branched polyunsaturated hydrocarbons inPseudomonas maltophilia

SummaryThe hydrocarbon composition ofPseudomonas maltophilia was determined by gas chromatography-mass spectrometry. Mono-, di- and tri-unsaturated alkenes were identified with a predominance of polyunsaturated components. The carbon chains of the alkenes contained single methyl branches iniso andanteiso position and double methyl branches in theiso-iso andanteiso-anteiso configurations. The composition of the hydrocarbons from cells grown in synthetic media enriched with amino acids or volatile fatty acids demonstrated that the probable precursors incorporated into individual hydrocarbons were branched and normal fatty acid chains in the range from C3 to C16. The probable fatty acid precursors which were connected together to form the major triunsaturated hydrocarbon chains were two monounsaturated chains, whereas the major liunsaturated chains resulted from condensation of saturated and monounsaturated chains. The probable precursors for the major monounsaturated hydrocarbons were C14 (C15) and C16 (C15) fatty acids. The accumulation of hydrocarbons was not detected until the cells were in the late exponential phase of growth; the maximal levels were reached at the mid-stationary phase of growth.

The pyrolytic release experiment - Measurement of carbon assimilation

The pyrolytic release experiment is one of the three life detection tests to be conducted on the 1976 Viking Lander Missions. In this experiment minimal assumptions are made about the nature of possible life forms. Such species are assumed to have adapted to the aridity of contemporary Mars. It is also assumed that any biological cycle on Mars would be initiated by the assimilation of atmospheric CO2 or CO. Both gases are known constituents of the Martian atmosphere. Hypothetical carbon cycles are proposed and methods for measuring their primary producers are described.In the operation of the pyrolytic release experiment on Mars, the assimilation of14CO2 and/or14CO will be measured using samples of surface soil incubated under a close simulation of ambient conditions. The incubation can be performed in the light or in the dark with or without added water vapor. Pyrolytic analysis measures the extent of14C-assimilation into organic constituents of microorganisms in the soil. Presumptive evidence of biological activity would be verified by a control analysis with dry heat sterilized soil. Descriptions are given of the test programs used to ascertain the soundness of this analytical approach. The operational sequences of the flight instrument are briefly discussed.

Enhancement of polyether biodegradation in activated sludge following exposure to conditioning agents

Abstract Activated sludge exposed to C18 unsaturated fatty acid diesters of polyethylene glycol (PEG) acquires the ability to degrade PEG of average molecular weight (Afn) 1,000, 1,450, 3,350 but not 8,000. Likewise, a polypropylene glycol (PPG) diester of oleic acid enhances the degradation of PPG Afn 1,025. An analogous enhancement in PEG degradative activity is effected by pre‐exposure to polyoxyethylene oleyl monoether. Enhancement of degradation is restricted to polyethers which are the same kind as used in the pretreatment; for example, samples pre‐exposed to PEG unsaturated diester are unable to degrade PPG. Thin layer chromatographic analysis of PEG incubations indicates disappearance of PEGs from the supernatant without a noticeable change in the molecular weight of remaining PEGs. Removal of these compounds from the supernatants occurs well before catabolic CO2 evolution is completed. Since there were negligible increases in the biomass and acetylesterase activity resulting from the catabolism o...

Biodegradation of petroleum chemical extinguisher in soil enhances the degradation of polyethylene glycol

Abstract Petroleum Chemical Extinguisher ®(PCE) is polyethylene glycol(PEG) diester of fatty acid used in extinguishing fires and cleaning up oil spills. When PCE is added to garden soil, the amount of CO3 evolved indicates a near complete mineralization. Negligible increases in microbial biomass and acetylesterase activity resulted from PCE catabolism. PCE‐exposed soil has enhanced activity to degrade PEG of average molecular weight 400, 1, 000 or 1, 450 but not 3, 350. Potential uses of PCE in promoting biodegradation of PEG pollutants are discussed.